Electrical fuse



J. C. REA

ELECTRICAL FUSE Feb. 9, 1932.

Filed Dec. 2, 1950 11W mHM James Maf y? A TTORNEYS.

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Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE JAMES C. REA, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO PACIFIC ELECTRIC MANUFACTURING CORPORATION, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALIFORNIA ELECTRICAL FUSE Application led December 2, 1930. Serial No. 499,481.

This invention relates generally to electrical fuses such as are generally employed for protectinor electrical circuits, and particularly fuses which are used in connection with high tension electrical distribution lines.

It is a general object of the invention to devise improved-means for making convenient electrical connection between the fuse links of an electrical fuse, and the fuse Contact or terminal members.

It is a further object of the invention to devise an electrical fuse having a refill assembly provided with novel metallic members adapted to make automatic electrical connection with the contact members of the fuse, when the refill assembly is placed in normal operating position.

It is a further object of the invention to devise an improved fuse construction utilizing explosive charges or capsules to insure positive blowout in case of an overload.

F urther objects of the invention will appear from the following description in which I have set forth the preferred embodiments of the present invention. It is to be understood that the appended claims are to be accorded a range of equivalents consistent with the state of the prior art.

Referring to the drawings:

Figure 1 is a side elevational view in cross section, illustrating a fuse constructed in accordance with the present invention.

Fig. 2 is a side elevational view partly in cross section illustrating a refill assembly for the device of Fig. 1.

Fig. 3 is a cross sectional detail taken along the line 3-3 of Fig. 1.

Fig. 4 is a view similar to Fig. 1 showing' a modification of the invention.

That form of the invention illustrated in Fig. 1 consists of a tubular member 10, which is preferably made of some suitable insulating material, such as a phenolic condensate product. Suitable terminals or contact members 11 are mounted upon the ends of this tube 10. The contact members 11 are provided with openings or passages 12, which are preferably alined with and of substantially the same diameter as the passage thru tubular member 10.

For economic reasons I prefer to incorporate the elements within tube 10 in a fuse assembly such as shown in Fig. 2. This fuse assembly in its preferred form consists of a v tube 13, which can be made of suitable insulating material, and which forms a liner for tubular member 10 when the refill is in normal operating position. lVit-liin the tube 13 there is a suitable fuse link or wire 14 which is proportioned or made of material consistent with the desired current carrying capacity of the fuse. Conductor leads 15 which are preferably flexible, extend inwardly from the ends of tube 13 and have their inner ends connected to fuse link 14. The outer ends of leads 16 extend thru closures or plugs 17 mounted in the ends of tubes 13, and which are made of suitable material such as cork.

The space within tube 13 is preferably packed with a suitable filler 18 of divided insulating material, such as crushed marble.

In order to make convenient electrical connection between conductor leads 16 and contact member 11, the outer ends of these leads are connected to resilient metalic members 21. The construction of these resilient members appears more clearly in Fig. Each member is formed of a flat strip or ribbon of spring metal, such as copper, bronze or brass, having one portion 23 thereof bent to embrace the associated lead conductor 16. Good electrical connection can be formed by soldering portion 23 to the lead conductor, or by crimping gagement. Portion 24 of the spring strip is bentv arcuate in form as shown, and is integrally connected with portion 23, by the outwardly extending portion 26. When compressed a certain amount, portion 24 can be,

readily inserted in passage 12 of an associated Contact member 11, so as to normally tend to expand against the inner walls of the same. Thus when members 21 are in normal operating position, they tend to expand to form good electrical contact with contact members 11. The ends of the fuse can be normally closed by removable caps 25 frictionally engaged over the ends of contact members 11.

In the refill assembly described above, explosive means is desirable in order to insure portion 23 to form a tight frictional ena positive interruption of the circuit in case of slight overloads. Thus adjacent each end of tube 13, I provide a capsule or charge 27 of explosive material, such as gunpowder. To ignite these charges automatically, I provide a resistance wire 28 which extends thru both the capsules 27, and which is connected at its ends to the conductor leads 1G so as to V be in shunt with the fuse links 111. The pertion of resistance wire 28 extending 'between capsules 27, is preferably loosely enclosed by a tube or sheath 29, which is preferably of insulating material. sheath 29 can be formed byY what is commonly terminal insulating spaghetti. Y

WV hen the fuse described above is in operation, melting of fuse link 1a because of a slight overload causes a relatively heavy momentary'current to flow thru the resistance wire 28. Capsules 27 are' thus immediately ignited, andthe following explosion blows the closure 17 and spring strips 21 outwardly thru contact members 11, carrying with them the conductor leads 16. Thus the conductor leads are immediately jerked apart thus interrupting any arc which may tend to form between the inner ends of these leads. Fusion of resistance wire 28 within the sheath or tube 29 will also ignite or assist in ignition of capsules 27, since' such fusion will be accompanied by the projection of jets of incandescent material i'rom the ends of tubes 29 upon the capsules 27. After fuse has blown, the liner tube 13 together with any remaining filler 18 can be slid longitudinally from tubular member 10, and a new refill assembly as shown in Fig. 2, can be inserted. In inserting this relill assembly, it is only necessary to slightly compress the advancing member 21 to cause the refill to enter one of the Contact members 11. Continue-d inner movement of Athe reiill will then position the same as shown in Fig. 1 with the strip members 21 in electrical Contact with Contact members 11,y and caps 25 can be applied to the ends of the fuse. It will be notedthat members 21 'serve not only to make electrical connection between conductor leads 16 and contact members 11, but also serve as abutments against which closures 17 press, when the fuse is being blown. Y

That modification of the invention shown .in Fig. 4 is substantially the same as that de- A suitable tube orassembly adapted to be slipped into lsaid tubular member, said assembly comprising a fuse element, and resilient metallic members connected to said element and adapted to resiliently expand against the inner walls of said Contact members when the assembly is operablyY positioned within the tubular member.

2. In an electrical fuse,a tubular member, hollow contact members mounted on the ends of said tubular members,-the openings in said contact members being alined with andV of substantially the same diameter as the passage thru the tubular member, and a refill assembly adapted to be slipped into said tubular member, said assembly comprising a liner tube slightly smaller in diameter than the diameter ofthe passage thru the tubular member, a fuse element disposed within said liner tube, and resilient metallic members connected to the said element, said resilient members being adapted to resiliently expand against the inner walls of the contact members when the Yassembly is operably positioned within said tubular member.

3. In an electrical Jfuse, a tubular member, Contact members mounted upon the ends of the tubular member, one of said members having an opening therethrough alined with the passage thru said tubular member, a metallic spring clip disposed within said one contact member, said clip comprising a flat strip of resilient metal bent to resiliently eXpand in contact with the inner walls of said one contact member, and a fuse element connected to said clip and to the other contact member.'

In testimony whereof, I have hereuntoset 

